"This being proved, it is evident that these sedimentary formations, whose strata present themselves upon the slopes of mountains, in inclined or vertical directions, existed before these mountains arose. The formations of the same class that are prolonged horizontally, until they meet the same slopes, must be on the contrary of a date posterior to the formation of the mountain; for it cannot be conceived, that, in rising from the mass of the earth, it should not have elevated at the same time all previously existing strata.
"Let us introduce proper names into the general and simple theory which we have developed, and the discovery of M. de Beaumont will be announced.
"Of the four species of sedimentary formations that we have distinguished, three, and these are the uppermost, the nearest to the surface of the globe, or the most modern, extend in horizontal layers, from the Cote d'Or and from Forez, to the mountains of Saxony; and only one, which is the oolite or limestone of Jura, shows itself elevated within this district.
"Therefore the Hartz, the Cote d'Or, and Mount Pilus of Forez, have risen from the globe since the formation of the Jura oolite, and before the deposit of the three other formations.
"On the slopes of the Pyrenees and Appennines, two of the formations are raised up, namely, the oolite and the greensand and chalk; the tertiary formations, and the diluvium that covers them, have preserved their primitive horizontality. The Pyrenees and Appennines are, therefore, more modern than the limestone of Jura, and the greensand which they have raised, and more ancient than the tertiary strata and the diluvium.
"The western Alps, and among them Mount Blanc, have, like the Pyrenees, raised the limestone of Jura, and the greensand, but, in addition, they have also raised the tertiary formations; the diluvium is alone horizontal in the vicinity of these mountains.
"The date of the elevation of Mount Blanc must, therefore, inevitably be placed between the epoch of the formation of the tertiary strata and the diluvium.
"Finally, upon the sides of the central Alps, (Mount St. Gothard,) and of the mountains of Ventorix and Liberon, near Avignon, no one of the sedimentary formations is horizontal; all the four have been raised up. When these mountains arose, the diluvium itself must have already been deposited."
"The sedimentary formations appear, from their nature, and the regular disposition of their layers, to have been deposited in times of tranquillity. Each of these formations being characterized by a particular system of organized beings, both vegetable and animal, it is indispensable to suppose, that between the epochs of tranquillity, corresponding to the precipitation of two of these overlying formations, there must have been a great physical revolution upon the globe. We now know that these revolutions have consisted in, or at least been characterized by, the raising of a system of mountains. The two first liftings-up pointed out by M. de Beaumont, not being by any means the greatest of the four he has succeeded in classing, it will be seen that we cannot infer that the globe, in growing older, becomes less fit to experience this species of catastrophe, and that the present period of tranquillity may not be terminated like those that have preceded it, by the elevation of some immense mountain chain."
M. de Beaumont next attempted, by a fancied arrangement of zones and parallels to great circles, to classify the mountains he had not an opportunity of examining, with those in respect to which he had obtained the above satisfactory conclusions. We fear, however, that he has proceeded to theorize too speedily, and before he had obtained a sufficient number of facts. We are certain, that in respect to the great Alleghany group of the United States, which he classes with the Pyrenees and Appennines, he must be mistaken, for no formations later than the transition limestone are to be found in their vicinity. In respect to the highlands of the state of New-York, and their branch of primitive rocks, which extends along the Hudson to the island of New-York, the sandstone of New-Jersey appears to continue horizontally until it reaches their bases, and no rocks appear to have been raised on the south-eastern side of the highlands, which are the easternmost of the five parallel ridges of the Alleghanies, older than the slate; but on their north-western side the transition limestone appears to have been raised. They therefore are older than any mountains examined by M. de Beaumont, and were we to hazard a conjecture, we should class them with the Grampians of Scotland, and the mountains of Wales, in both of which slate is the only rock of the transition series that appears to have been elevated.